
Multi-Service Access Device For Channelized Interfaces
Telecom Standard Product Data Sheet
Production
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990823, Issue 4
591
14.22.1 Mixed Payload (STS-12c, STS-3c, and STS-1)
Each PRGM is designed to process the payload of a STS-12/STM-4 frame in a time-multiplexed
manner. Each time division (12 STS-1 paths) can be programmed to a granularity of a STS-1. It
is possible to process one STS-12c/STM-4c, twelve STS-1/STM-0 or four STS-3c/STM-1 or a
mix of STS-1/STM-0 and STS-3c/STM-1 as long as the aggregate data rate is not more than one
STS-12/STM-4 equivalent. The mixed payload configuration can support the three STS-1/STM-
0 and STS-3c/STM-1 combinations shown below:
Three STS-1/STM-0 with three STS-3c/STM-1
Six STS-1/STM-0 with two STS-3c/STM-1
Nine STS-1/STM-0 with one STS-3c/STM-1.
The STS-1 path that each one of the payload occupies, cannot be chosen randomly. They must be
placed on STS-3c/STM-1 boundaries (group of three STS-1). See Table 7 and Table 9 for more
details.
14.22.2 Synchronization
Before being able to monitor the correctness of the PRBS payload, the monitor must synchronize
to the incoming PRBS. The process of synchronization involves synchronizing the monitoring
LFSR to the transmitting LFSR. Once the two are synchronized the monitoring LFSR is able to
generate the next expected PRBS bytes. When receiving sequential PRBS bytes (STS-12c/VC-4-
4c), the LFSR state is determined after receiving 3 PRBS bytes (24 bits of the sequence). The last
23 of 24 bits (excluding MSB of first received byte) would give the complete LFSR state. The 8
newly generated LFSR bits after a shift by 8 (last 8 XOR products) will produce the next
expected PRBS byte.
In master/slave configuration of the monitor (STS-48c/VC-4-16c concatenated payloads) more
bytes are needed to recover the LFSR state, because the slaves needs a few bytes to be
synchronized with the J1 byte indicator.
The implemented algorithm requires four PRBS bytes of the same payload to ascertain the LFSR
state. From this recovered LFSR state the next expected PRBS byte is calculated.
An Out of Synchronization and Synchronized State is defined for the monitor. While in progress
of synchronizing to the incoming PRBS stream, the monitor is out of synchronization and
remains in this state until the LFSR state is recovered and the state has been verified by receiving
4 consecutive PRBS bytes without error. The monitor will then change to the Synchronized State
and remains in that state until forced to resynchronize via the RESYNC register bit or upon
receiving 3 erred bytes. When forced to resynchronize, the monitor changes to the Out of
Synchronization State and tries to regain synchronization.
It is important to note that the monitor can falsely synchronize to an all zero pattern or, if the
incoming pattern is inverted, an all ones pattern. It is recommended that users poll the PRGM
Monitor’s LFSR value after synchronization has been declared to confirm that the value is neither
all 1’s or all 0’s.